A series of randomized trials is proposed to be conducted by subgroups of ten clinical centers in Phase I of a cooperative agreement with NHLBI to test the feasibility of providing, and obtaining compliance with selected nutritional and behavioral non-pharmacologic interventions in a population with high normal blood pressure and to measure the short term effectiveness of the non-pharmacologic interventions on reducing or preventing an increase in DBP. This phase is done in preparation for a Phase II single randomized control trial involving all ten centers to test whether a single optimal regimen of non-pharmacologic intervention can reduce the incidence of definite hypertension (defined as a sustained DBP of 90mmHG or greater or the initiation of treatment with antihypertensive drugs by a personal physician). Final decision on the various specific interventions to be tested in Phase I and the final single optimal regimen in Phase II will be made by the Steering Committee. In Phase I, the Boston center proposes to screen over 3,000 persons aged 25 to 49 years to identify 200 eligible participants with untreated DBP from 78-89 on a three stage screen, with weights from 105-160% of ideal weight, and free of medical or other exclusions. In the example interventions posed by the Boston center for Phase I, a multifactorial dietary program based on a calorie restricted modification of the American Heart Association Phase II diet aimed at weight reduction of at least 5% of body weight, will be compared with a program of regular vigorous exercise using a 2x2 factorial design: diet only, exercise only, diet-exercise, and neither, to assess whether either of these interventions alone or in combination result in a significant lowering of DBP as compared to control. In Phase II, the Boston center proposes to screen over 6,000 persons to identify 400 persons eligible to be randomized in the Phase II trial of a single optimal regimen of non-pharmacologic intervention to reduce the incidence of hypertension. If successful, this program could be of great public health significance since 20% of the adult population in the U.S. has hypertension which is associated with significantly elevated risk of heart attack, stroke, premature death and other morbidity.